The fuel for use in internal combustion engines and heating systems is usually filtered before being fed to the engine or heating system. Filters are necessary because the presence of contaminants, such as water, in fuel systems has been found to be particularly disadvantageous for running efficiency of the machine that is using the fuel. For instance, as in the case with diesel or gasoline engines in boats or land vehicles, the presence of water in the fuel may cause corrosion of the fuel injector system with consequent reduction of the efficiency thereof and eventual complete breakdown thereof. Additionally, water in fuel systems may present a dangerous situation when power from an engine is necessary and water in the fuel results in the inability to deliver power at a crucial point in the operation of the engine.
In the past, various types of conventional fuel filters have been used in order to separate and/or remove water from the fuel prior to feeding the engine. These conventional fuel filters typically include a casing made of glass or steel that is mounted underneath a bracket having a fuel inlet and a fuel outlet and a filter element that is accommodated within the casing. The fuel introduced from the fuel inlet flows down a central passageway and enters the casing through a lower opening. The fuel changes flow direction to ascend in the casing and is filtered by the filter element and sent to the engine through the fuel outlet. In these conventional fuel filters, a major part of the water content included in the fuel may fall by gravity when the fuel flows from the opening. When the fuel is reversed in direction to flow upwardly, the remainder of the water content may attach to the surface of the filter element and accumulate to form droplets, which fall and gather in the bottom of the casing. A very small amount of water may pass through the filter element but such a small amount of water is very easily fully burned in the engine and typically does not affect engine efficiency. The water gathering in the bottom part of the casing may be removed at a suitable maintenance interval.
Drawbacks have been found in such conventional fuel filters. For instance, since a large amount of water may attach to the surface of the filter element and accumulate thereon when the filter is in use, the surface of the filter element applied with water gathering treatment or water repellant treatment is gradually attacked by the water over a period of time so that the life of the filter element is shortened. Furthermore, as a recent requirement especially related to exhaust gas purification, it is necessary to remove the water in the fuel to substantially zero in order to accurately maintain the measuring of the fuel amount at the fuel injection valve. From this requirement, it is necessary to separate the water content in the fuel as completely as possible before reaching the filter element.
An additional disadvantage to conventional fuel filters has been realized in regards to the water content accumulated in the bottom part of the casing of the fuel filter that has had to be manually removed at certain regular intervals. It has been found that if the water removing process is forgotten, the water level may reach the lower surface of the filter element wherein not only does the filter efficiency deteriorate but a large amount of water may be sent to the engine together with the fuel. This has an especially detrimentally effect when the filter element is old and the filtering function has deteriorated wherein the water sent to the engine may cause rust to be introduced into the fuel injection system or may lead to other major efficiency decreases in engine production.
In light of these drawbacks of conventional fuel filtering systems, various apparatuses have been designed to attempt to resolve these negative characteristics by alerting the user of the presence of water and/or automatically draining collected water from the fuel system.
U.S. Pat. No. 4,276,161 to Matsui et al. discloses a fuel filter with a water level detector having an electrode provided at a bottom part of the casing of the fuel filter forming a detecting gap with the metal body of the casing. The sensor responds to water level in the casing so that should the water level in the casing of the fuel filter reach a predetermined level, a low resistance condition between the electrode and casing is detected by a water level detecting circuit. The sensor of Matsui et al. requires a strong current passing through the sensor and is a passive sensor that does not allow programmability of the water level for use with varying types of fuel systems or machines.
U.S. Pat. No. 4,562,431 and corresponding U.K. Patent Application No. GB 2,121,187 to Jahnke et al. disclose a motor fuel filter equipped for water separation by interrupting or greatly reducing the current passing through the sensor after the sensor has given a signal indicating the presence of water in sufficient quantity to require draining soon. The sensor system of Jahnke et al. is a passive system that does not allow for water level threshold programmability for the use with varying types of fuel systems.
U.S. Pat. No. 4,619,764 to Church et al. is directed to a filter assembly and associated filter unit including a repelling action filter media for use in vacuum or suction side fuel filter applications. The filter unit is a screw-on unit with centrally located threads at opposite ends of the filter unit and with a specifically designed end cap allowing use of the filter unit with a dual zone collection bowl normally used for coalescing pressure side filter applications. The end cap includes holes which allows use of both of the collection zones in spite of the normal isolation between the collection zones. The sensor disclosed in Church et al. is a passive level sensor that does not allow for variable water level threshold programmability.
U.S. Pat. No. 5,213,682 to Richardson discloses a fuel supply system including a probe device mounted in an outlet passage of a filter head and having probe elements extending into a filter unit which is removably engaged with the head. Also disclosed is circuitry in the device responsive to contact with water in the filter to complete a circuit and actuate a signal to indicate the presence of such water. The water detection sensor of Richardson is installed in a standard fuel filter and is related to a passive water detection system that does not allow variable programmability of threshold water levels.
U.K. Patent Application No. GB 2,065,336 to Mackenzie is directed to a device for discharging water and/or air contaminant from a mineral oil contaminant separator or from a mineral oil reservoir and separator having such a device. This system includes a vent valve or pump that is automatically opened when a first probe detects the presence of contaminant and which remains open for a prescribed time after the contaminant is cleared. A second probe is provided which gives an alarm indication and that also energizes the motor valve that may operate for a longer period than the first valve. The sensors disclosed in Mackenzie are asymmetrical and are passive sensors that do not allow for variable programmability of water level thresholds.
European Patent Application No. EP 0715873 to Biere et al. discloses a fuel/water separator including an all sheet metal shell having a bottom which is secured to a metal adaptor plate enabling a drain valve and a water detector to be attached to the bottom of the shell. The sensors disclosed in Biere et al. are utilized with metallic filter elements and do not allow for the variable programmability of water level thresholds.
Finally, PCT Application No. WO 01/33069 to Girondi is directed to a unit for automatically bleeding off water which separates in a vehicle fuel filter wherein the unit comprises a sensor means positioned in the collection chamber to undergo activation when the water level reaches a predetermined maximum value. There is also provided an electrically operated withdrawal device connected to the vehicle electrical system to withdraw the water separated within the collection chamber through the bleed outlet or to close the outlet. A microprocessor is also provided connected to the sensor means and to the switch means of the vehicle electrical power system, to electrically power the withdraw device when the sensor means is activated and the ignition key is in a first activation position. The sensor disclosed in Girondi utilizes a flow mechanism for activating the withdraw device at a certain level. This sensor system does not allow for the variable programmability of water level thresholds determined by a probe system.
The prior art fuel filter alarm systems have numerous disadvantages. For instance, the sensor systems of prior art devices have not allowed for the contaminant level of varying thresholds to be readily changed depending on the size engine utilizing the fuel filter system. Mainly, the fuel filter systems of the prior art have had to be designed specifically for varying sized engines that can accommodate varying levels of water contamination. This has required that dealers stock numerous sizes of the fuel filter sensor mechanisms in order to satisfy all customer requirements. Additional disadvantages of prior art systems have included the placement of the fuel filter apparatuses in disadvantageous locations within the engine that prevent the user from approaching the fuel filter and/or removing the water within the fuel filter. Another disadvantage is that while some prior art devices warn about the existence of water, they do not readily offer the capability for water removal which can result in the malfunction of the engine.
As such, there remains the need for the creation of a contaminant detection system for use in fuel systems of internal combustion engines, heating systems, and the like wherein the unit can be placed easily between the fuel reservoir and the engine, the unit can give the capability of warning about the existence of water or other contaminant in the fuel, and can also allow the removal of the contaminant with only temporary pause of the operation of the engine.
There additionally remains the need for a programmable variable sensor system that can be readily preprogrammed to varying levels of contaminant or water levels that would allow the deployment of the same water sensing circuit with fuel filter systems developed for different sized engines where the capacity of the fuel filter can differ significantly.